U.S. patent application number 15/728539 was filed with the patent office on 2018-07-12 for moving end electronic detection of secondary load path engagement of aircraft flight control actuator.
The applicant listed for this patent is Parker-Hannifin Corporation. Invention is credited to Abbas M. Charafeddine, Derek James Olson.
Application Number | 20180194454 15/728539 |
Document ID | / |
Family ID | 62781877 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180194454 |
Kind Code |
A1 |
Olson; Derek James ; et
al. |
July 12, 2018 |
MOVING END ELECTRONIC DETECTION OF SECONDARY LOAD PATH ENGAGEMENT
OF AIRCRAFT FLIGHT CONTROL ACTUATOR
Abstract
A linear actuator, for controlling movement of a control surface
of an aircraft, includes a screw, a primary load path and secondary
nut engaged with the screw, and an engagement member. The
engagement member moves from an ambush position, maintained by the
primary load path or the secondary nut, to an engaged position,
restricting relative movement between the primary load path and the
secondary nut. The restricted relative movement may occur in
response to free relative axial movement of the primary load path
and the secondary nut caused by a failure of the primary load path
of the linear actuator. A sensor of the linear actuator is
configured to sense the failure of the primary load path and the
free relative axial movement of the primary load path and the
secondary nut.
Inventors: |
Olson; Derek James; (Ogden,
UT) ; Charafeddine; Abbas M.; (Mission Viejo,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Parker-Hannifin Corporation |
Cleveland |
OH |
US |
|
|
Family ID: |
62781877 |
Appl. No.: |
15/728539 |
Filed: |
October 10, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62444486 |
Jan 10, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64C 9/14 20130101; B64C
5/02 20130101; B64C 5/10 20130101; B64C 13/28 20130101; B64C 13/341
20180101; B64C 2009/005 20130101 |
International
Class: |
B64C 13/28 20060101
B64C013/28 |
Claims
1. A linear actuator for controlling movement of an external
surface, the linear actuator comprising: a screw; a primary load
path engaged between the screw and the external surface, the
primary load path having a primary nut engaged with the screw; a
secondary nut engaged with the screw; and an engagement member that
is maintained by one or both of the primary load path or the
secondary nut in an ambush position until relative axial movement
of the primary load path and the secondary nut exceeds a
predetermined amount, after which the engagement member is free to
move from the ambush position to an engaged position restricting
relative movement between the primary load path and the secondary
nut.
2. The linear actuator of claim 1, wherein the engagement member is
carried by the secondary nut for axial common movement
therewith.
3. The linear actuator of claim 1, wherein the linear actuator
includes a biasing member that biases the engagement member towards
the engaged position.
4. The linear actuator of claim 3, wherein the biasing member
extends between the engagement member and the secondary nut.
5. The linear actuator of claim 1, wherein the engagement member is
maintained in the ambush position via the relative positioning of
the secondary nut relative to the primary load path.
6. The linear actuator of claim 1, wherein the engagement member is
maintained in the ambush position via axial alignment of each of
the primary load path and the secondary nut relative to one another
and to the screw.
7. The linear actuator of claim 1, wherein the engagement member is
biased radially inwardly towards a central rotational axis of the
screw to the engaged position.
8. The linear actuator of claim 1, wherein the secondary nut is
anti-rotated relative to the screw via contact with a secondary nut
housing disposed about the secondary nut and axially fixed relative
to the primary load path.
9. The linear actuator of claim 1, wherein the primary nut is
anti-rotated relative to the screw via coupling to the external
surface.
10. The linear actuator of claim 1, further including a sensor for
sensing movement of the engagement member from the ambush position
to the engaged position.
11. The linear actuator of claim 10, wherein the sensor is carried
for common axial movement with the primary load path.
12. The linear actuator of claim 10, wherein the sensor is fixed
relative to the secondary nut upon movement of the engagement
member to the engaged position.
13. The linear actuator of claim 1, further in combination with an
aircraft having the external surface, wherein the secondary nut is
coupled to the external surface for controlling the external
surface when the engagement member is in the engaged position.
14. A linear actuator for controlling a control surface, the linear
actuator comprising: a screw; a primary load path extendable
between the screw and the control surface; and a secondary load
path extendable between the screw and the control surface, wherein
the secondary load path transitions from a default non-controlling
state having less than majority control of the control surface to a
secondary controlling state to take majority control of the control
surface in response to the primary load path transitioning from a
default operative state having majority control of the control
surface to a failure state having less then majority control of the
control surface.
15. The linear actuator of claim 14, wherein the primary load path
transfers a greater load between the screw and the control surface
than the secondary load path when the primary load path is in the
default operative state, and wherein the secondary load path
transfers a greater load between the screw and the control surface
than the primary load path when the secondary load path is in the
secondary controlling state.
16. The linear actuator of claim 14, wherein the linear actuator
further includes a sensor configured to sense both the transition
of the primary load path from the default operative state to the
failure state, and the transition of the secondary load path from
the default non-controlling state to the secondary controlling
state.
17. The linear actuator of claim 14, wherein the secondary load
path includes a secondary nut threadedly engaged with the screw,
and the primary load path includes a primary nut threadedly engaged
to the screw, and wherein the secondary nut is configured to
transfer a lesser force from the screw to the control surface than
the primary nut until the primary load path is transitioned to the
failure state.
18. The linear actuator of claim 17, wherein the secondary load
path is biased in the non-controlling state until relative axial
movement of the primary load path and the secondary nut exceeds a
predetermined amount.
19. The linear actuator of claim 17, wherein the secondary load
path further includes an engagement member coupled to the secondary
nut for translation with the secondary nut, the engagement member
being configured to move from a default disengaged position to a
biased engaged position in response to the primary load path
transitioning to the failure state, and the movement of the
engagement member to the biased engaged position enabling the
secondary load path to transition to the secondary controlling
state.
20. The linear actuator of claim 14, further in combination with an
aircraft having the control surface, wherein the primary load path
provides majority control of the control surface when the secondary
load path is in the default non-controlling state.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/444,486 filed Jan. 10, 2017, which is hereby
incorporated herein by reference in its entirety.
FIELD OF INVENTION
[0002] The present invention relates generally to aircraft flight
control actuators, and more particularly to aircraft flight control
actuators having assemblies for restricting and detecting movement
of a flight control surface in the case of an actuator failure.
BACKGROUND
[0003] Aircraft typically include a plurality of flight control
surfaces that, when controllably positioned, guide the movement of
the aircraft from one destination to another. The number and type
of flight control surfaces included in an aircraft may vary, but
typically include both primary flight control surfaces and
secondary flight control surfaces. The primary flight control
surfaces are those that are used to control aircraft movement in
the pitch, yaw and roll axes, and the secondary flight control
surfaces are those that are used to influence the lift or drag (or
both) of the aircraft. Although some aircraft may include
additional control surfaces, the primary flight control surfaces
typically include a pair of elevators, a pair of ailerons and a
rudder, and the secondary flight control surfaces typically include
a horizontal stabilizer, a plurality of flaps, slats and
spoilers.
[0004] Modern aircraft have horizontal stabilizers located at the
tail section of the fuselage or the rudder section that are
pivotally supported relative to the airplane fuselage to "trim" the
aircraft during flight by selective adjustment by the operator or
pilot from an internal control unit. This involves adjusting the
position of the horizontal stabilizer by a stabilizer actuator to
accommodate different load distributions within the aircraft and
different atmospheric conditions, i.e. wind, rain, snow, etc. In
this regard the stabilizer is traditionally pivotally connected to
the tail section of the fuselage at a point generally midway along
its length.
[0005] One common trimmable horizontal stabilizer actuator consists
of a primary ball nut connected with an actuating drive gimbal
which is pivotally connected to an actuating end of the horizontal
stabilizer structure. The primary ball nut includes a primary ball
nut threaded member and a primary drive gimbal. A rotatable ball
screw extends axially and usually vertically through the primary
ball nut threaded member and the drive gimbal. The primary ball nut
is connected to the stabilizer by trunnion segments of the primary
drive gimbal. The ball screw, in turn, may have a remote end
opposite the driving end, where the remote end is remote from the
actuating drive gimbal and may be fixed from translation or axial
movement. For example, the remote end may be connected to a second,
support gimbal which is pivotally secured to the aircraft, such as
to the tail section.
[0006] As the ball screw is rotated, the primary drive gimbal and
primary ball nut will be moved in translation. Thus, as the ball
screw is rotated in one direction, the primary ball nut is moved
towards the ball screw distal end and the leading edge of the
horizontal stabilizer is pivoted in a first direction, such as
upward. On the other hand, by rotating the ball screw in an
opposite direction, the primary ball nut is moved toward the ball
screw proximal end and the leading edge of the horizontal
stabilizer is pivoted in a second direction, such as downward.
Rotation of the ball screw is routinely effected by a motor and
associated gearing which is actuated by the pilot via the internal
control unit.
[0007] The horizontal stabilizer movement, as controlled by the
operator, is transmitted by the ball screw through the actuating
primary drive gimbal by way of the primary ball nut which together
define a primary load path. The movement has a load with tensile
and compressive components as well as a torque component due to the
ball screw thread lead. Failures of the primary load path, such as
caused by the shearing off of a connecting trunnion segment of the
primary drive gimbal, or by the loss of nut ball members from the
primary ball nut, can result in the partial or complete loss of
control of the horizontal stabilizer. For this reason, stabilizer
actuators are often provided with a secondary load path as a
protection against such catastrophic failure of the primary load
path.
SUMMARY OF INVENTION
[0008] The present invention provides a linear actuator for moving
a control surface, such as of an aircraft, the linear actuator
having cooperating primary and secondary load paths each extending
between a screw of the linear actuator and the control surface,
where the secondary load path transitions to a controlling state
taking majority control of the control surface from the primary
load path in response to a failure of the primary load path. A
sensor of the linear actuator is configured to sense both the
failure of the primary load path and the transitioning of the
secondary load path.
[0009] The present invention also provides a linear actuator having
a screw, a primary load path including a primary nut engaged with
the screw, a secondary nut engaged with the screw, and an
engagement member. The engagement member moves from an ambush
position maintained by the primary load path or the secondary nut
to an engaged position restricting relative movement between the
primary load path and the secondary nut, in response to relative
axial movement of the primary load path and the secondary nut that
is caused by a failure of the primary load path of the linear
actuator.
[0010] According to a first aspect, a linear actuator for
controlling movement of an external surface includes a screw, a
primary load path engaged between the screw and the external
surface, the primary load path having a primary nut engaged with
the screw, a secondary nut engaged with the screw, and an
engagement member that is maintained by one or both of the primary
load path or the secondary nut in an ambush position until relative
axial movement of the primary load path and the secondary nut
exceeds a predetermined amount, after which the engagement member
is free to move from the ambush position to an engaged position
restricting relative movement between the primary load path and the
secondary nut.
[0011] The engagement member may be carried by the secondary nut
for axial common movement therewith.
[0012] The linear actuator may further include a biasing member
that biases the engagement member towards the engaged position.
[0013] The biasing member may extend between the engagement member
and the secondary nut.
[0014] The engagement member may be maintained in the ambush
position via the relative positioning of the secondary nut relative
to the primary load path.
[0015] The engagement member may be maintained in the ambush
position via axial alignment of each of the primary load path and
the secondary nut relative to one another and to the screw.
[0016] The engagement member may be biased radially inwardly
towards a central rotational axis of the screw to the engaged
position.
[0017] The secondary nut may be anti-rotated relative to the screw
via contact with a secondary nut housing disposed about the
secondary nut and axially fixed relative to the primary load
path.
[0018] The primary nut may be anti-rotated relative to the screw
via coupling to the external surface.
[0019] The linear actuator may further include a sensor for sensing
movement of the engagement member from the ambush position to the
engaged position.
[0020] The sensor may be carried for common axial movement with the
primary load path.
[0021] The sensor may be fixed relative to the secondary nut upon
movement of the engagement member to the engaged position.
[0022] The linear actuator may be provided in combination with an
aircraft having the external surface, where the secondary nut is
coupled to the external surface for controlling the external
surface when the engagement member is in the engaged position.
[0023] According to a second aspect, a linear actuator, for
controlling a control surface, includes a screw, a primary load
path extendable between the screw and the control surface, and a
secondary load path extendable between the screw and the control
surface. The secondary load path transitions from a default
non-controlling state having less than majority control of the
control surface to a secondary controlling state to take majority
control of the control surface in response to the primary load path
transitioning from a default operative state having majority
control of the control surface to a failure state having less then
majority control of the control surface.
[0024] The primary load path may transfer a greater load between
the screw and the control surface than the secondary load path when
the primary load path is in the default operative state, and the
secondary load path may transfer a greater load between the screw
and the control surface than the primary load path when the
secondary load path is in the secondary controlling state.
[0025] The linear actuator may further include a sensor configured
to sense both the transition of the primary load path from the
default operative state to the failure state, and the transition of
the secondary load path from the default non-controlling state to
the secondary controlling state.
[0026] The secondary load path may include a secondary nut
threadedly engaged with the screw, and the primary load path
includes a primary nut threadedly engaged to the screw, and the
secondary nut may be configured to transfer a lesser force from the
screw to the control surface than the primary nut until the primary
load path is transitioned to the failure state.
[0027] The secondary load path may be biased in the non-controlling
state until relative axial movement of the primary load path and
the secondary nut exceeds a predetermined amount.
[0028] The secondary load path may further include an engagement
member coupled to the secondary nut for translation with the
secondary nut, the engagement member being configured to move from
a default disengaged position to a biased engaged position in
response to the primary load path transitioning to the failure
state, and the movement of the engagement member to the biased
engaged position enabling the secondary load path to transition to
the secondary controlling state.
[0029] The linear actuator may be provided in combination with an
aircraft having the control surface, where the primary load path
provides majority control of the control surface when the secondary
load path is in the default non-controlling state.
[0030] The foregoing and other features of the invention are
hereinafter described in greater detail with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The annexed drawings, which are not necessarily to scale,
show various aspects of the disclosure.
[0032] FIG. 1 is an elevational view of an aircraft that includes
an actuator according to the present invention.
[0033] FIG. 2 is a schematic view of an actuator according to the
present invention, for moving a control surface of the aircraft of
FIG. 1.
[0034] FIG. 3 is a partial elevational schematic view of the
actuator as shown in FIG. 2, broken away in section.
[0035] FIG. 4 is a sectioned view of the actuator as shown in FIG.
3.
[0036] FIG. 5 is a sectioned view of the actuator as shown in FIG.
4.
[0037] FIG. 6 is a partial elevational schematic view of the
actuator as shown in FIG. 2, broken away in section, and shown with
the moving end of the actuator in a partial failure state.
[0038] FIG. 7 is a partial elevational schematic view of the
actuator as shown in FIG. 2, broken away in section, and shown with
the moving end of the actuator in another partial failure
state.
DETAILED DESCRIPTION
[0039] The principles of the present invention have particular
application to flight control actuators for controlling a flight
control surface of a vehicle, such as a stabilizer of an aircraft.
The principles are also applicable to other actuators including
linear and rotary actuators where there is a need to restrict
relative movement of actuator components or to restrict actuator
movement due to external forces acting on the actuator, such as to
resist moving the actuator in forward and reverse directions caused
by external vibrational forces. The forward and reverse directions
may be linear directions in the case of a linear actuator or
rotational directions in the case of a rotary actuator.
[0040] Referring first to FIG. 1, an exemplary aircraft 10 includes
a rear fuselage 12 having a tail fin 14 which carries a rudder 16.
Horizontal stabilizers 18 and elevators 19 are provided on either
side of the tail fin 14. Each horizontal stabilizer 18 is pivotably
mounted to the fuselage 12 at pivot point 20 whereby it can be
pivoted about axis 22 to adjust the longitudinal pitch (i.e.,
"trim") of the aircraft 10. During flight, each horizontal
stabilizer 18 is adjusted by a horizontal stabilizer trim actuator
(also herein referred to as an HSTA) which moves the stabilizer's
leading edge 24 in a first direction, such as upward with respect
to FIG. 1 (aircraft nose down) and in a second direction, such as
downward with respect to FIG. 1 (aircraft nose up). The stabilizer
adjustments may be automatically controlled directly from the
aircraft's flight computers (for example, an automatic flight
control unit, or any automatic control unit in other applications)
and/or may be manually controlled by pilot input.
[0041] Turning now to FIG. 2, an exemplary horizontal stabilizer
trim actuator (HSTA) 100 according to the present invention is
shown for selectively controlling the position of the horizontal
stabilizer 18 (or a control surface, more generally). The actuator
100 is configured to control movement of the horizontal stabilizer,
for example in response to a command from a controller 101 to move
the flight control surface 18. As mentioned, the flight control
surface 18 is rotatable about the pivot axis 22, in an upward first
direction A or a downward second direction B. It will be
appreciated that apparatuses such as an internal control unit 101
are generally well known in the art and thus known details thereof
have been omitted for purposes of brevity and simplicity.
[0042] The horizontal stabilizer 18 may be pivotably connected
along its length to a pivoting stabilizer gimbal structure 102,
also herein referred to as a stabilizer gimbal 102. The stabilizer
gimbal 102 is attached to the vertical stabilizer section or
fuselage tail section 103 of the fuselage 12. The leading edge 24
of the horizontal stabilizer 18, also herein referred to as the
control surface 18, may be in turn pivotably connected to an
actuating drive gimbal 104 located generally midway along the
actuator 100 and which in turn is pivotably connected to a rotating
assembly of the actuator 100, such as a threaded nut and screw
assembly, to be further discussed in detail.
[0043] Referring now to FIGS. 2-4, the illustrated actuator 100 is
shown as a linear actuator that is driven to effect movement of at
least a portion of the stabilizer 18 (or a driven component in
other applications) along a longitudinal axis 105. The actuator 100
includes a screw 106 that extends between a moving end 108 (also
herein referred to as an actuating end) of the actuator 100 and a
fixed end 110 (also herein referred to as a remote end) of the
actuator 100 opposite the moving end 108. The moving end 108 moves
to control movement of the stabilizer 18 via coupling to the drive
gimbal 104.
[0044] The fixed end 110 is coupled to a reference structure of the
aircraft (such as a fuselage portion) via a support gimbal 112.
Further details of connection of stabilizer actuators to the rudder
section or to the fuselage tail section 103 of the fuselage 12 have
been omitted for purposes of brevity and simplicity.
[0045] As used herein, coupling may refer to direct coupling
between elements or indirect coupling between elements, where a
third element is disposed between the coupled elements.
[0046] The moving end 108 of the illustrated actuator 100 is
configured to extend and retract thereby moving a force transfer
member 114. The force transfer member 114 extends from the control
surface 18 and is coupled between the drive gimbal 104 and the
control surface 18. The force transfer member 114 may be integral
with or otherwise suitably coupled to the control surface 18. The
force transfer member 114 couples a suitable location of the
actuator 100, such as the drive gimbal 104, to the stabilizer 18
for allowing driving and control of the control surface/stabilizer
18 via the actuator 100.
[0047] Particularly, the primary load path of the actuator 100 is
the default load path along which load is transferred between
control surface 18 and the screw 106 of the actuator 100 to
control, such as to restrict movement of, the control surface 18.
In a default state of the actuator 100, the primary load path is in
a controlling state having majority control over the control
surface 18.
[0048] The primary load path is shown at 115 in FIG. 3, and extends
between the screw 106 and the transfer member 114. As illustrated,
the transfer member 114 extends along an axis orthogonal to a plane
of the page. The primary load path includes a primary ball nut
assembly 116, also herein referred to as a primary nut assembly
116, which is located generally midway along the screw 106. An
extend mechanical stop 120 may be attached to a distal end 122 of
the screw 106 to prevent the primary ball nut assembly 116 from
being unthreaded relative to the screw 106.
[0049] The primary ball nut assembly 116 includes is a primary ball
nut threaded member 128, a plurality of ball members 130 contained
in the primary ball nut threaded member 128 via one or more ball
plugs 131, and the actuating drive gimbal 104. It will be
appreciated that the depicted screw 106 is a ball screw 106 having
threads for receiving the plurality of ball members 130.
[0050] Alternatively, it will be appreciated that in some
embodiments the screw 106 may not be a ball screw and may instead
have alternative threading, and that a non-ball nut may be utilized
in place of the primary ball nut assembly 116. For example, the
principles of the invention are also applicable to an actuator
having a drive screw, a lead screw, or a roller screw, or to an
actuator having a translating screw and a rotating nut. For
example, in some embodiments, the nut may be rotated by the motor
to effect translation of a screw.
[0051] The screw 106 is driven to effect movement of the control
surface 18 via effecting translational movement of the primary ball
nut assembly 116 along the screw 106. Translation of primary ball
nut assembly 116 is along a longitudinal axis 124 of the ball screw
106. The translation is effected by rotation of the ball screw 106
about the same axis 124. Via the rotation of the ball screw 106,
the primary ball nut assembly 116 and the force transfer member 114
are movable in an upward third direction C (corresponding to
movement of the stabilizer 18 in the downward second direction B)
and an opposite downward fourth direction D (corresponding to
movement of the stabilizer 18 in the upward first direction A).
[0052] As used herein, the upward and downward directions refer to
one alignment of the HSTA 100 in the fuselage of an aircraft, where
in level flight or landed on a ground surface, an HSTA is often
aligned vertically with respect to the ground surface. Thus, a
downward/distal end of the HSTA is located nearer the ground than
the opposite upward/proximal end of the HSTA. In other words, in
such orientation, upward is meant to refer to a direction towards a
proximal end 126 of the screw 106 adjacent the support gimbal 112.
Downward is meant to refer to a direction towards the distal end
122 of the screw 106 adjacent the extend mechanical stop 120. The
terms are not meant to be limiting, but refer to opposing
directions along the longitudinal axis 124, which could be
otherwise aligned, for example relative to the ground, fuselage, or
control/control surface 18. In another embodiment, the HSTA 100
could be reversed 180 degrees.
[0053] The illustrated primary ball nut threaded member 128, also
herein referred to as the primary nut threaded member 128, is
coupled to the force transfer member 114/control surface 18 via the
drive gimbal 104. The drive gimbal 104 includes a primary nut
housing 134 disposed about the primary nut threaded member 128,
primary nut trunnions 136 gimballing the primary nut threaded
member 128 to the primary nut housing 134, and primary nut housing
trunnions 138 gimballing the primary nut housing 134 to the force
transfer member 114.
[0054] Two primary nut trunnions 136 are disposed opposite one
another about the primary nut threaded member 128. The primary nut
trunnions 136 are shown as integral with the primary nut threaded
member 128, though may be a separate component coupled to the
primary nut threaded member 128 in any suitable manner in other
embodiments. A ball member 135 is coupled to each of the primary
nut trunnions 136 and is received in a channeled member (not shown)
coupled to the primary nut housing 134.
[0055] Two primary nut housing trunnions 138 are disposed opposite
one another about the primary nut housing 134. The primary nut
housing trunnions 138 are shown as separate from but coupled to the
primary nut housing 134. A ball member 137 is coupled to each of
the primary nut housing trunnions 138 and is received in a
channeled member 139 coupled to the primary nut housing 134. The
primary nut housing trunnions 138 are also coupled to the transfer
member 114, such as via one or more fasteners 141.
[0056] It will be appreciated that the illustration of FIG. 3 shows
only one manner and location of fastening. Additional or
alternative manners and/or locations could be used where
suitable.
[0057] The primary nut threaded member 128 is anti-rotated relative
to the screw 106 via its connection to the primary nut housing 134
(primary nut trunnions 136, ball members 135 and associated
channeled members), and subsequently via the connection of the
primary nut housing 134 to the force transfer member 114 (primary
nut housing trunnions 138, ball members 137 and associated
channeled members 139).
[0058] It will be appreciated that in some embodiments, the primary
nut housing 134 and primary nut housing trunnions 138 may be
omitted, and the primary nut trunnions 136 may be gimballed to the
transfer member 114. It will also be appreciated that although the
primary nut housing 134 is shown disposed fully circumferentially
about the primary nut threaded member 128 in FIG. 3, the primary
nut housing 134 may be not fully disposed about the primary nut
threaded member 128 in some embodiments.
[0059] The corresponding movements of the primary ball nut threaded
member 128 and the ball screw 106 are effected by a drive unit 142.
The drive unit 142 is disposed at the fixed end 110 of the actuator
100 and includes for example, a hydraulic or electric drive motor
144 and a gearbox assembly 146. The drive motor 144 is provided for
rotatably driving the screw 106 to effect the translation of the
primary nut threaded member 128 and subsequent movement of the
control surface 18. The drive unit 142 and further details thereof
are of a construction well known in the art and thus it is only
generally shown and described for purposes of simplicity and
brevity.
[0060] It will be appreciated that the drive motor 144 need not be
an electric motor. The drive unit 142 could additionally or
alternatively comprise hydraulic and/or pneumatic cylinders, or any
other device which can effect movement of the primary nut threaded
member 128 and the control surface 18.
[0061] Referring next to FIGS. 2-5, a secondary nut 160 is also
coupled to the ball screw 106, and, along with a secondary drive
gimbal 161, forms a secondary load path 163. The secondary load
path 163, like the primary load path 115, extends between the drive
screw 106 and the force transfer member 114. In the case of failure
of the primary load path 115, the secondary load path 163 is
configured to provide a majority of control of the control surface
18 via a transfer of force from the drive unit 142, along the
secondary load path 163.
[0062] As indicated, the secondary load path 163 includes the
secondary nut 160, and also includes the secondary drive gimbal
161. The secondary drive gimbal 161 includes a secondary nut
housing 162 gimballed to a secondary gimbal sleeve 165 by one or
more secondary nut housing carriage members 164, and secondary nut
trunnions 167 gimballing the secondary gimbal sleeve 165 to the
force transfer member 114.
[0063] Two secondary nut trunnions 167 are disposed opposite one
another about the secondary gimbal sleeve 165. The secondary nut
trunnions 167 are shown as separate from but coupled to the
secondary gimbal sleeve 165. The secondary nut trunnions 167 are
also coupled to the force transfer member, 114 such as via the
fasteners 141.
[0064] It will be appreciated that in some embodiments, different
fasteners may be used to couple the secondary nut trunnions 167 to
the force transfer member 114 than are used to couple the primary
nut housing trunnions 138 to the force transfer member 114.
Further, it will be appreciated that the illustration of FIG. 3
shows only one manner and location of fastening. Additional or
alternative manners and/or locations could be used where
suitable.
[0065] The secondary gimbal sleeve 165 extends fully
circumferentially about and is radially outwardly spaced from the
primary nut housing 134. Two opposing secondary nut housing
carriage members 164 gimbal the secondary gimbal sleeve 165 to the
secondary nut housing 162. The carriage members 164 are shown as
integral with the secondary nut housing 162, though they may be
separate and coupled to the secondary nut housing 162 in other
embodiments.
[0066] The secondary nut housing 162 is disposed circumferentially,
such as fully circumferentially, about the secondary nut 160. In
other embodiments, the secondary nut housing 162 may extend less
than fully circumferentially about the secondary nut 160 where
suitable.
[0067] In the default operative state of the HSTA 100, the
secondary drive gimbal 161 is fixed relative to the primary ball
nut assembly 116. In such default state, the secondary nut housing
162 and secondary gimbal sleeve 165 are caused to translate with
the primary ball nut assembly 116 along the screw 106 via force
applied to the primary nut threaded member 128 from the threads of
the screw 106.
[0068] The secondary nut 160, like the primary nut threaded member
128, is threadedly engaged with the screw 106. As depicted, the
secondary nut 160 includes at least one thread for engaging the
screw 106 and lacks ball members. The secondary nut 160 may have
inverse threading or other suitable threading for engaging
corresponding threads of the ball screw 106.
[0069] Referring briefly to FIG. 5, the secondary nut 160 is
anti-rotated relative to the screw 106 such that that secondary nut
160 is caused to translate along the screw 106 upon rotation of the
screw 106 about the longitudinal axis 124. Engagement of the
secondary nut 160 with the secondary nut housing 162 provides for
this anti-rotation. Particularly, the outer circumference of the
secondary nut 160 is shaped, such as having flats 166, for engaging
corresponding features on the secondary nut housing 162.
[0070] As depicted, two oppositely disposed flats 166 are provided
on the outer circumference of the secondary nut 160 for engaging
with and preventing rotation of the secondary nut 160 relative to
the secondary nut housing 162. One or more flats 166 may be
included in other embodiments, and the flats 166 may be otherwise
suitably circumferentially separated from one another about the
secondary nut 160.
[0071] Referring again to FIGS. 2-5, the secondary nut 160 and the
secondary load path 163 does not provide majority control of the
force transfer member 114 and the control surface 18 during default
operative functioning of the primary load path 115. This is because
the primary load path 115 in the default operative state, also
herein referred to as the default controlling state, transfers a
greater load between the screw 106 and the control surface 18 than
the secondary load path 163. Thus in its default operative state,
the primary load path 115 has majority control.
[0072] In the default operative state of the primary load path 115,
the secondary load path 163 is in a default non-controlling state
in which the secondary load path 163 has less than majority control
of the control surface 18. In the default non-controlling state of
the secondary load path 163, the secondary nut 160 is caused to
translate in the same direction that the primary nut threaded
member 128 translates in response to rotation of the screw 106.
[0073] The secondary nut 160 is axially-spaced at opposed axial
ends of the secondary nut 160 from the secondary nut housing 162 in
this default non-controlling state of the secondary load path 163.
In this way, axial force is not directly axially-transferred
between the secondary nut 160 and the secondary nut housing 162.
Further, the secondary nut 160 is defaultly axially-positioned a
predetermined distance from the primary nut threaded member 128,
and thus from the primary ball nut assembly 116, via the default
axial alignment of the secondary nut 160 along the screw 106. It
will be appreciated that the predetermined distance may be a single
distance or a range.
[0074] The secondary nut 160 is configured to transfer a lesser
force than the primary ball nut assembly 116 from the screw 106 to
the control surface 18, until a failure of the primary load path
115 effects relative axial movement of the primary ball nut
assembly 116 and the secondary nut 160 relative to one another and
a distance between the primary ball nut assembly 116 and the
secondary nut 160 exceeds a predetermined amount.
[0075] In the case of a failure of the primary load path 115
(failure of the primary ball nut assembly 116), and transition of
the primary load path 115 from its default controlling state to a
failure state having less than majority control of the control
surface 18, a change of the secondary load path 163 is effected. In
such case, the secondary load path 163 is transitioned from its
default non-controlling state to a secondary controlling state
taking majority control of the control surface 18 from the primary
ball nut assembly 116 and the primary load path 115. The secondary
load path 163 then transfers a greater load between the screw 106
and the control surface 18 than the primary load path 115.
[0076] The secondary load path 163 is configured to take this
majority control upon numerous failure modes of the primary load
path 115. One failure of the primary load 115 path may be caused by
a fracturing or shearing off of a connecting trunnion segment 136
or 138 of the primary ball nut assembly 116. In such case, the
force transfer member 114 will no longer be controlled by the
primary threaded member 128. The primary nut housing 134, the force
transfer member 114, the secondary gimbal sleeve 165 and the
secondary nut housing 162 may move relative to the secondary nut
160. Another failure of the primary load path 115 may be the
fracturing or loss of one or more ball members 135 or 137, causing
similar relative movement.
[0077] Yet another failure of the primary load path 115 may be the
loss of nut ball members 130 from the primary nut threaded member
128, such as due to loss or breaking of a ball plug 131. In such
case, the primary nut threaded member 128, the primary nut housing
134, the force transfer member 114, the secondary gimbal sleeve 165
and the secondary nut housing 162 may move relative to the
secondary nut 160.
[0078] For example, turning to FIG. 6, a failure mode of the
primary load path 115 is depicted such as where one or more ball
members 135 or 137 has been damaged or where one or more trunnion
segments 136 or 138 have been damaged. The primary nut housing 134,
the force transfer member 114, the secondary gimbal sleeve 165 and
the secondary nut housing 162 were thus enabled to freely shift
along the screw 106 relative to the threadedly engaged secondary
nut 160. Upon this free shifting of one or more components of the
primary ball nut assembly 116 relative to the secondary nut 160, in
this case towards the remote end 110 of the HSTA 100, the secondary
nut 160 is restricted.
[0079] Particularly, an engagement member 170 is configured to be
moved to a position axially aligned between the primary ball nut
assembly 116 and the secondary nut 160, and more specifically
between the secondary nut 160 and the secondary nut housing 162, to
allow for the secondary load path 163 to take majority control of
the control surface 18 from the failed primary load path 115. The
engagement member 170 is configured to be moved when relative axial
movement of one or more components of the primary ball nut assembly
116 and the secondary nut 160 exceeds a predetermined amount
allowing the engagement member 170 to move from a default ambush
position (FIG. 4) to a biased engaged position (FIG. 6).
[0080] Turning now to specifics of the engagement member 170, the
engagement member 170 is coupled to the secondary nut 160 for being
carried for axial translation therewith. Opposing engagement
members 170 are shown, though any suitable number, one or more, of
engagement members 170 may be included, and/or the engagement
members 170 may be otherwise circumferentially arranged about the
secondary nut 160 in other embodiments.
[0081] The HST actuator 100, and particularly the secondary load
path 163, includes a biasing member 172, such as a leaf spring,
that is coupled between the engagement member 170 and the secondary
nut 160, such as via a coupling portion 173 coupled to the
secondary nut 160. The biasing member 172 biases the engagement
member 170 radially inwardly towards the longitudinal axis 124,
into the biased engaged position (FIG. 6) in axial alignment
between the secondary nut 160 and the secondary nut housing
162.
[0082] The engagement member 172 is maintained in the ambush
position (FIG. 4), spaced from the engaged position (FIG. 6), such
as radially outwardly from the engaged position. The ambush
position (FIG. 4) is maintained against the bias of the biasing
member 172 by one or both of the primary load path 115 and the
secondary nut 160, and more particularly by relative positioning
of, such as axial alignment of, the secondary nut 160 relative to
the components of the primary load path 115.
[0083] As depicted in FIG. 4, when relative axial movement of the
primary load path 115 and the secondary nut 160 has not exceeded a
predetermined amount (when the primary load path 115 is in the
default operative controlling state and the secondary load path 163
is in the corresponding default non-controlling state) the
engagement member 172 is disposed in engagement with an axially,
inwardly-projecting shelf 174 of the secondary nut housing 162. On
the other hand, when the shelf 174 is caused to move relative to
the secondary nut 160, such as away from secondary nut 160 (in the
direction C of FIG. 2), the engagement member 170 is able to move
off of the shelf 174 and to its biased engaged position.
[0084] As depicted in FIG. 6, the primary nut housing 134 has at
least partially uncoupled from the primary nut threaded member 128,
enabling the force transfer member 114 and the secondary nut
housing 162 coupled thereto to freely shift toward the remote end
110 of the HSTA 100. It follows that when the engagement member 170
is in the engaged position, load may be transferred from the screw
106 to the secondary nut 160, and then to the secondary nut housing
162 and the force transfer member 114. Thus movement of the
engagement member 170 to the biased engaged position enables the
secondary load path 163 to transition to its secondary controlling
state.
[0085] It will be appreciated that in some embodiments, the
secondary nut housing 162 and the engagement member 170 may be
constructed such that the engagement member 170 is biased in the
non-axially-engaged position. In such case, a projection, such as a
shelf 174, of the secondary nut housing 162 may move or cam the
engagement member 170 into the axially-engaged position restricting
relative movement of the secondary nut 160 and the primary load
path 115.
[0086] Still referring to FIG. 6, it is noted that the engagement
members 170 each include an orifice 176 extending partially through
the respective engagement member 170, or as depicted, fully through
the engagement member 170. This feature may be provided to enable a
suitable tool to be inserted into the engagement member 170 to
allow for removal from the biased engaged position of the
engagement member 170 that is shown in FIG. 6. The engagement
members 170 may be accessed through one or more passages 180 in the
secondary nut housing 162 that are aligned with the engaged
positions of the engagement members 170.
[0087] As shown, sensors 184 occupy the one or more passages 180
and are coupled to the secondary nut housing 162 in the passages
180. The sensors 184 may be removed to obtain access to the
respective orifices 176 of the engagement members 170. Via coupling
to the secondary nut housing 162, the sensors 184 are carried for
common axial movement with the secondary nut housing 162 and with
the force transfer member 114. In the default controlling state of
the primary load path 115, the sensors 184 are also carried for
common movement with the primary load path. The sensors 184 are
fixed relative to the secondary nut 160 upon transition of the
engagement members 170 to the engaged position.
[0088] The linear HST actuator 100 includes one or more sensors 184
for sensing movement of the one or more engagement members 170 from
the ambush position to the engaged position. The depicted sensors
184 are configured to sense the movement of the engagement members
170. The movement signifies failure of the primary ball nut
assembly 116 of the primary load path 115, the transition of the
primary load path 115 from the default operative state to the
failure state, and the transition of the secondary load path 163
from the default non-controlling state to the secondary controlling
state.
[0089] The sensors 184 may be any suitable type of sensors such as
binary position sensors for sensing a near condition and a far
condition of the respective engagement members 170. Two sensors 184
are depicted disposed opposite one another and aligned at the
location of the engaged positions of the two engagement members
170. Where lesser or more engagement members 170 are used in other
embodiments, a corresponding number of sensors 184 may be
included.
[0090] Turning now to FIG. 7, a second example of a failure mode of
the primary load path 115 is depicted, also such as where one or
more ball members 135 or 137 has been damaged or where one or more
trunnion segments 136 or 138 have been damaged. The primary nut
housing 134, the force transfer member 114, the secondary gimbal
sleeve 165 and the secondary nut housing 162 were thus enabled to
freely shift along the screw 106 relative to the threadedly engaged
secondary nut 160. Different from the depiction and failure mode of
FIG. 6, the free shifting of one or more components of the primary
ball nut assembly 116 relative to the secondary nut 160 is in a
direction towards the distal end 122 of the HSTA 100.
[0091] In this direction, the secondary load path 163 will hold
load but has not yet transitioned to its secondary controlling
state. Rather, because a failure of the primary load path has
caused the primary nut housing 134, the secondary gimbal sleeve 165
and the secondary nut housing 162 to move in the direction D of
FIG. 2, the engagement members 170 are maintained on the shelves
174.
[0092] It will be appreciated that due to the failure of the
primary load path 115, external force on the control surface 18,
such as air pressure in the case of an aircraft, can cause the
primary ball nut assembly 116 to freely shift oppositely in the
direction C of FIG. 2, and thus effect transition of the secondary
load path 163 into the state shown in FIG. 6, where the engagement
member 170 is moved to the biased engaged state and the secondary
load path 163 is transitioned to the secondary controlling
state.
[0093] It will also be appreciated that the HSTA 100 in other
embodiments may include one or more additional engagement members
170 disposed axially opposite the depicted engagement members 170
along the longitudinal axis 124, at an axially opposite side of the
secondary nut 160. In this manner, the secondary load path 163 may
transition to the secondary controlling state in response to
movement of the failed primary ball nut assembly 116 and primary
load path 115 that effects free shifting of the force transfer
member 114 in either axial direction C or D of FIG. 2.
[0094] In summary, a linear actuator 100, for controlling movement
of a control surface 18 of an aircraft 10, includes a screw 106, a
primary load path 115 and secondary nut 160 engaged with the screw
106, and an engagement member 170. The engagement member 170 moves
from an ambush position, maintained by the primary load path 115 or
the secondary nut 160, to an engaged position, restricting relative
movement between the primary load path 115 and the secondary nut
160. The restricted relative movement may occur in response to free
relative axial movement of the primary load path 115 and the
secondary nut 160 caused by a failure of the primary load path 115
of the linear actuator 100. A sensor 184 of the linear actuator 100
is configured to sense the failure of the primary load path 115 and
the free relative axial movement of the primary load path 115 and
the secondary nut 160.
[0095] Although the invention has been shown and described with
respect to a certain embodiment or embodiments, it is obvious that
equivalent alterations and modifications will occur to others
skilled in the art upon the reading and understanding of this
specification and the annexed drawings. In particular regard to the
various functions performed by the above described elements
(components, assemblies, devices, compositions, etc.), the terms
(including a reference to a "means") used to describe such elements
are intended to correspond, unless otherwise indicated, to any
element which performs the specified function of the described
element (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary embodiment or
embodiments of the invention. In addition, while a particular
feature of the invention may have been described above with respect
to only one or more of several illustrated embodiments, such
feature may be combined with one or more other features of the
other embodiments, as may be desired and advantageous for any given
or particular application.
* * * * *